THE RELATIVE roles of genetic and environmental influences in the etiology of multiple
sclerosis have not yet been assessed with certainty. The well established familial tendency
of the disease, which can scarcely be explained away by such theories as that of" common
exposure", 1 implies that a genetic factor might be important. On the other hand,
environmental factors are suggested by the unique epidemiologic features of the disease,
the evidence for an immune reaction (frequent elevation of γ-globulin in the cerebrospinal …